Hello Glenn Maxwell
Thank you for contacting Microsoft community
To do this, I will recommend the following steps:
- Locate the Organizational Unit (OU) where your 250 Active Directory (AD) groups are stored.
- In the Properties window, go to the "Security" tab and click add to add the users you want to grant permissions to
- To assign permissions, click on "Advanced" to open the Advanced Security Settings window.
- Assign the required permissions
- In the Advanced Security Settings window, click on "Add" to add specific permissions for the user/group.
- In the Permission Entry window, click on "Select a principal" and select the user/group again.
- Under "Apply onto", select "This object and all descendant objects" to apply the permissions to all objects within the OU.
- Click "OK" to apply the permission.